Atomic oxygen abundance toward Sgr B2

Previous Infrared Space Observatory (ISO) observations suggest that a significant fraction of oxygen in even denser, translucent clouds may be in atomic form.

We have analyzed velocity-resolved archival SOFIA observations of the 63um fine-structure [OI] transition toward the high-mass star-forming region Sgr B2(M) in the Central Molecular Zone. The foreground spiral-arm clouds as well as the extended Sgr B2 envelope between the Sun and the background dust continuum source produce multiple [OI] absorption components, spectrally separated in velocity space. The gas-phase atomic oxygen column density in foreground clouds toward Sgr B2 is well correlated with the total hydrogen column density, with an average atomic oxygen abundance of (2.51+/-0.69)x10^-4^ with respect to hydrogen nuclei.